1. Field of the Invention
The present invention relates to a transmission that ensures synchronization of the rotational speed of the shaft and the rotational speed of a gear during shifting gears by reducing the rotational speed of the shaft.
2. Description of the Related Art
In an automatic transmission mechanism that uses a conventional manual transmission, synchronization of the rotational speed of the shaft and the rotational speed of a gear during speed reduction is performed by increasing the rotational speed of the shaft through revving by engine control, and the synchronization of the rotational speed of the shaft and the rotational speed of a gear during speed increase is performed by reducing the rotational speed of a shaft (input shaft) 51 by means of a braking mechanism 53 disposed on a countershaft (layshaft) 52 arranged in parallel with the input shaft 51, as shown in FIG. 3 (Refer to Japanese Patent Application Laid-open No. 2001-263472, for example).
This transmission 54 is an input reduction type transmission in which a speed reduction gear 55 is provided between the input shaft 51 and the layshaft 52 in a constant mesh manner, comprising a transmission gear pair composed of a plurality of layshaft gears 56 provided to a layshaft 52 and a plurality of output shaft gears 58 provided to an output shaft 57.
However, in addition to the input reduction type transmission described above, there are also output reduction type transmissions in which a speed reduction gear is provided between the output shaft and the layshaft in a constant mesh manner, comprising a transmission gear pair composed of a plurality of input shaft gears provided to an input shaft and a plurality of layshaft gears provided to a layshaft.
In the output reduction type transmission 59, the output shaft 69 and the layshaft 68 are connected so as to be constantly engaged, as shown in FIG. 4, so a braking mechanism cannot be provided to the layshaft 68 because the rotational force of the layshaft 68 is directly transmitted to the output shaft 69, in other words, the propeller shaft.
As a result, a mechanical synchromesh 65, in which conical surfaces 63 and 64 for coupling that mutually make contact during gear insertion are respectively formed on each coupling surface of a gear 61 and a hub 62, has been adopted.
However, this mechanical synchromesh 65 slides both conical surfaces 63 and 64 for coupling to synchronize the rotational speed, so a drawback exists in that the device is larger and costs are higher due to the greater number of components that require working for the gear 61 and hub 62. Furthermore, if the vehicle is a large vehicle, then application is difficult because the force applied to the mechanical synchromesh 65 is greater.